CVE-2020-26948 in Server
Summary
by MITRE • 10/11/2020
Emby Server before 4.5.0 allows SSRF via the Items/RemoteSearch/Image ImageURL parameter.
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Analysis
by VulDB Data Team • 11/18/2020
The vulnerability identified as CVE-2020-26948 represents a server-side request forgery flaw in Emby Server versions prior to 4.5.0, specifically affecting the Items/RemoteSearch/Image endpoint through the ImageURL parameter. This vulnerability falls under the category of insecure direct object references and allows attackers to manipulate the server into making unauthorized requests to internal or external systems. The flaw enables malicious actors to bypass normal access controls and potentially gain unauthorized access to internal network resources that would otherwise be protected by firewalls or network segmentation. The vulnerability is particularly concerning because it leverages the legitimate remote search functionality of Emby Server, which is designed to fetch images from external sources, but fails to properly validate or sanitize the input parameters.
The technical implementation of this vulnerability occurs when Emby Server processes the ImageURL parameter in the Items/RemoteSearch/Image endpoint without adequate validation of the provided URLs. Attackers can craft malicious URLs that point to internal network resources, localhost addresses, or other sensitive targets within the network infrastructure. This allows for potential reconnaissance activities where the server inadvertently reveals information about internal systems or services. The vulnerability can be exploited to perform various malicious activities including accessing internal services, bypassing authentication mechanisms, or even escalating privileges within the network. The flaw demonstrates poor input validation practices and highlights the importance of implementing proper sanitization and access control measures for all user-provided parameters.
The operational impact of CVE-2020-26948 extends beyond simple information disclosure, as it can enable attackers to perform more sophisticated attacks such as internal network scanning, service enumeration, and potentially privilege escalation. Organizations using Emby Server in environments with sensitive data or critical infrastructure face significant risks, particularly when the server is deployed in network segments that are not properly isolated. The vulnerability can be exploited by attackers with minimal technical expertise, making it a particularly dangerous flaw in enterprise environments. Additionally, the vulnerability can be combined with other attack vectors to create more complex exploitation scenarios, potentially leading to full system compromise. The impact is further amplified in cloud environments where Emby Server might be exposed to untrusted networks or where proper network segmentation is not implemented.
Security mitigations for this vulnerability include upgrading to Emby Server version 4.5.0 or later, which contains the necessary patches to address the SSRF flaw. Organizations should also implement network segmentation to isolate Emby Server instances from critical internal systems and deploy web application firewalls to monitor and filter incoming requests. Input validation and sanitization measures should be enforced at all levels of the application stack, ensuring that any user-provided URLs are properly validated against a whitelist of acceptable domains or patterns. Additionally, implementing proper access controls and limiting the server's ability to make outbound connections to internal resources can significantly reduce the attack surface. The vulnerability aligns with CWE-918, which describes server-side request forgery, and maps to ATT&CK technique T1190, which covers exploit public-facing application, making it a critical concern for organizations implementing security controls and monitoring systems.